1. Field of the Invention
The present invention relates to a photographing system constituted by a lens apparatus and an image pickup apparatus, and more particularly to a controlling apparatus for controlling a zoom operation in a photographing system such as a video camera, a still camera, or a monitoring camera.
2. Related Background Art
In many cases, a photographing system includes an optical-zooming function which changes a photographing field angle by moving a lens. In addition, some of the photographing systems have a digital-zooming function which electronically magnifies and reduces photographed image data. Besides, a photographing system has been proposed in which a zoom magnification virtually larger than a zoom magnification obtained in a case where an optical-zoom only is employed is obtained by using both the optical-zoom and the digital-zoom. In this regard, in Japanese Patent Application Laid-Open No. H09-243899 (paragraphs 0042 through 0046, FIG. 8, and the like), a technology in an interchangeable lens type photographing system in which zooming is carried out by smoothly shifting the optical-zoom and the digital-zoom from each other is proposed.
On the other hand, there is a professional-use photographing system which is equipped with a so-called preset zoom function (see Japanese Patent No. 3387889 (paragraphs 0027 through 0030, FIGS. 1 and 2, and the like)). The preset zoom function is a function in which an optical-zoom position is stored in a memory in advance and a zoom operation to the stored optical-zoom position is performed when a preset zoom switch is operated at an arbitrary optical-zoom position. The preset zoom function is convenient in a case where a zoom operation to a prescribed zooming position at a constant speed is repeated many times.
In addition, in Japanese Patent No. 3372912 (paragraph 0036, FIG. 1, and the like), the photographing system including a so-called shuttle shot zoom function is disclosed. The shuttle shot zoom function is an enhanced preset zoom function. That is, with the shuttle shot zoom function, when the preset zoom switch is operated at an arbitrary optical-zoom position, the arbitrary optical-zoom position is stored in the memory. After that, in accordance with the termination of preset zoom operation to a zoom position which is preset or an interruption of operation of the preset zoom switch during the preset zoom operation, the zooming operation to an original zoom position is performed by inverting the direction of zooming.
This function is used, for example, in a case where a tele-photo end is stored in the memory in advance, and a photographer wants to check whether a lens is focused or not after determining a composition at the arbitrary zoom position. In other words, the shuttle shot zoom function is convenient in a case where the zooming is performed once to the tele-photo end to confirm whether or not the lens is focused and then the zoom position is returned to an original position to start photographing, and where the photographing is performed alternately at arbitrary two zoom positions.
However, the preset zoom function and the shuttle shot zoom function which are mentioned above (hereinafter, both of them are referred to collectively as memory zoom function; and the operation thereof is hereinafter referred to as a memory zoom operation) are functions related to the optical-zoom. In the memory zoom function, the digital-zoom is not considered.
In this regard, it is inconvenient that the memory zoom function mentioned above can be used only in an optical-zoom region in the photographing system in which a large zoom magnification can be obtained by a combination of the optical-zoom and the digital-zoom.